A176797 Antiharmonic means of divisors of antiharmonic numbers.

1, 3, 7, 11, 13, 21, 21, 43, 35, 43, 61, 63, 85, 111, 77, 157, 91, 129, 119, 147, 185, 171, 273, 183, 255, 343, 231, 301, 245, 255, 333, 313, 507, 301, 455, 481, 521, 425, 471, 547, 473, 455, 813, 441, 931, 629, 559

Offset: 1

Author

Jaroslav Krizek, Apr 26 2010

Keywords

• nonn
• look

Comments

Values of sigma_2(n) / sigma(n) corresponding to terms of A020487(n), where sigma_2(n) is the sum of squares of divisors of n (A001157) and sigma(n) is the sum of the divisors of n (A000203).

Examples

			For n = 4; a(4) = 11 because A020487(4) = 16; A001157(16) = 341, A000203(n) = 31, antiharmonic means of divisors of 16 = 341 / 31 = 11.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Programs

Mathematica

Select[DivisorSigma[2, #]/DivisorSigma[1, #] & /@ Range[1000], IntegerQ] (* Amiram Eldar, Sep 18 2019 *)

Formula

a(n) = (A001157(A020487(n))) / (A000203(A020487(n))).